Intermediate beams are used to divide an elevator shaft vertically into two or more parts forming channels for separate cars moving along guide rails attached to the intermediate beams. Guide rails attached to intermediate beams can also be used to mount counterweights or to accommodate an elevator car in an oversized shaft.
The guide rails for elevator cars or counterweights are secured on the intermediate beams by welding, using various bars and/or plates to connect the vertical rails to the horizontal intermediate beams, which in turn are secured by welding their ends on mounting racks provided on opposite walls of the shaft or by casting the beams in the wall structure during the building stage.
The drawbacks of the previously known procedures for the mounting of guide rails include the difficulty of adjustment of the guide rails due to the rigid welded joints, and the precision requirements imposed by the installation safety condiderations on the person performing the welding, who generally has received special training as an elevator installer, not as a welder. In practice, it is necessary to take the rather large tolerances of the intermediate beams and associated mounting fixtures into account, which retards the installation of the guide rails. Further problems result from the difficulty of supplying electricity for the welding equipment to the required parts of the elevator shaft and the insufficient rigidity of the structures involved in the welding operations (intermediate beams of open cross-section, simple mounting lugs in the walls, etc.) as against the torsional load resulting from frictional forces and the normal forces of the guide load. This ultimately leads to the distortion of the guide rails and a bumpy elevator travel.